The aim of this project is to obtain structural information on polynucleotides and other polymers and to provide insights into the factors which control structure, principally through X-ray fiber diffraction and model building studies. Current areas include (1) correlation of the fiber structures of poly(rA).poly(dT) with solution and other properties by nondiffraction techniques; (2) a reexamination of poly(dA).poly(dT) by fiber diffraction techniques, (3) the test of a possible artefact in our earlier wet DNA fiber studies.